1. Field of the Invention
The present invention relates to water-based heat-expandable adhesive panels that contain solvent-free resins, and more particularly, to an environmentally friendly water-based heat-expandable adhesive panel that contains a water-based acrylic emulsion modified by a reactive emulsifier.
2. Description of Prior Art
A commercially available heat-releasable pressure-sensitive adhesive tape comprises a substrate, an organic resilient layer comparable to rubber resin and coated on the substrate, a resin adhesive layer having a blowing agent or a swelling agent and coated on the organic resilient layer, and a detachable release-film protective layer affixed to the surface of the resin adhesive layer.
However, the commercially available heat-releasable pressure-sensitive adhesive tape usually contains solvent-based resin and thus charges a large amount of solvent to the atmosphere during a processing process, thereby causing severe pollution and the greenhouse effect. In recent years, the greenhouse effect is becoming more severe. As a result, the resin synthesis industry is confronted with major issues, that is, reduction of volatile organic compound (VOC) emissions and the ultimate goal of energy saving and carbon reduction. In this regard, water-based resin is a potential Research & Development topic.
Acrylic emulsion plays a crucial role in water-based resin. To ensure the stability of emulsion particles and maintain the stability of acrylic emulsion, it is necessary to add emulsifiers to acrylic emulsion. However, the emulsifiers added to acrylic emulsion are of a low molecular weight and thus tend to permeate; as a result, the finished acrylic emulsion manifests deteriorated adhesiveness.
To overcome the aforesaid drawback of the prior art, the inventor of the present invention studies the adhesiveness of water-based acrylic emulsion resin and has discovered the following: acrylic emulsion remains stable when produced by polymerization of acrylic monomers in the presence of a reactive emulsifier; the reactive emulsifier enhances the adhesiveness and storage stability of water-based acrylic emulsion resin; and the water-based acrylic emulsion thus synthesized reduces VOC emissions and greenhouse effect and thus efficiently mitigates the impact of global warming.